<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* .item {
      color: red;
    } */

    /* 不是.why的元素 */
    .box :not(.why) {
      color: blue;
    }
  </style>
</head>
<body>

  <div class="box">
    <div class="item">列表内容1</div>
    <div class="item">列表内容2</div>
    <div class="why">列表内容3</div>
    <div class="item">列表内容4</div>
    <div class="item">列表内容5</div>
    <div>列表内容5</div>
    <div>列表内容5</div>
    <div>列表内容5</div>
  </div>

</body>
</html>